Dark current and 1/f noise characteristics of In0.74Ga0.26As photodiode passivated by SiNx/Al2O3 bilayer

•In0.74Ga0.26As photodiodes passivated with SiNx and SiNx/Al2O3 bilayer are fabricated.•Dark current and 1/f noise of photodiodes are investigated at different bias voltages and temperatures.•SiNx/Al2O3 bilayer effectively reduce the side current of photodiodes, especially for small photosensitive area.•SiNx/Al2O3 bilayer effectively reduce the 1/f noise of photodiodes, especially at low temperature.